This invention relates to a bending device for use, for example, in an endoscope.
As is well known, an endoscope comprises a hollow body, a flexible insertion portion extending from a front end of the body, a flexible bending portion extending from a distal end of the insertion portion, and a rigid portion provided at a distal end of the bending portion. An inspection window and an illumination window are formed at the rigid portion.
Japanese Utility Model Publication No. 9274/77 discloses a flexible tube structure for an endoscope which structure has one coil and a resilient thin plate. FIG. 1 of Japanese Laid-Open (Kokai) Utility Model Application No. 10605/80 shows an example in which this flexible tube structure is applied to a bending portion of an endoscope. More specifically, in the bending portion, the resilient thin plate is received in an internal space defined by the coil and extends in the longitudinal direction of the coil. Recesses are formed in each of opposite lateral edges of the resilient thin plate, and are juxtaposed in the longitudinal direction of this plate. The turn portions of the coil are engaged in the recesses. The bending portion is bent in a direction perpendicular to the resilient thin plate by an operating wire, so as to direct an inspection window and an illumination window of the rigid portion toward a desired direction.
The above bending portion is simple in construction, and can be easily manufactured, and particularly, this bending portion can be advantageously applied to the type of endoscope required to have a very narrow bending portion. However, in this bending device, a bending resistance possessed by the resilient thin plate can not be disregarded. For this reason, a reduction of the operating force has been limited. When a narrow operating wire is used to save the internal space, the lifetime of the operating wire is short.